Absorption and emission spectral studies of Eu~(3+)-doped PbO-PbF_2 glass system

摘要

Judd-Ofelt parameters obtained from the absorption spectra of Eu~(3+) ions doped in PbO-PbF_2 glasses are intermediate between the values for fluoride and phosphate glass matrices. Eu~(3+) ions are coordinated to both oxide and fluoride ions. The calculated transition probabilities (As~l) for the laser transition ~5D_0->~7F_2 are 171 and 170 for 30PbO-70PbF_2 and 70PbO-30PbF_2 glasses respectively and are significantly lower compared to phosphate glasses. The calculated (beta_Rcal) and experimental (beta_R expt) branching ratios for this transition show good agreement. The emission spectra display high energy transitions in the 440-570 nm region, a characteristic of parent matrices with low energy phonons such as the tellurite, germanate and fluoride glasses. The electron-phonon coupling strengths deduced from the excitation spectra of Eu~(3+) are 10.2 x 10~(-3) and 9.5 x l0~(-3) for 30PbO-70PbF_2 and 70PbO-30PbF_2 glasses respectively. The relative emission intensities of the low energy transitions to high energy transitions and the ratios of the most intense transitions ~5D_0 -> ~7F_2/~5D_0 ->~7F_1 significantly vary for the two glasses providing evidence for clustering of Eu~(3+) ions with increase in its concentration and increasing PbO content.